Association between Air Temperature and Acute Myocardial Infarction Hospitalizations in Tehran, Iran: A Time-Stratified CaseCrossover

BACKGROUND: Although the effect of temperature on the incidence of acute myocardial infarction (AMI) has been extensively documented, no study has previously investigated the association between temperature and AMI in the Middle Eastern countries. OBJECTIVE: To examine the association between daily mean temperature and AMI admission rates in Tehran, Iran. METHODS: Data on daily number of admissions of patients with AMI to Tehran hospitals between March 21, 2013 and March 19, 2016, were retrieved from the Iranian Myocardial Infarction Registry (IMIR). Over the same period, data on daily mean temperature and relative humidity were measured at Mehrabad International Airport weather station of the Islamic Republic of Iran Meteorological Organization. Time-stratified case-crossover design was employed to investigate the short-term association between the daily mean temperature and the number of daily admissions of patients with AMI, after adjusting for public holidays, relative humidity, and air pollution. RESULTS: An interquartile range (IQR) increase in daily mean temperature was associated with 15.1% (95% CI 1.3 to 30.8%) and 13% (95% CI 1.9% to 25.4%) increase in the risk of AMI hospitalizations during the entire year, and in the warm months of the year, respectively. There were no significant associations between IQR increase in the two-day cumulative average up to the six-day cumulative average of the daily mean temperature and AMI during the entire year, and warm or cold months of the year. CONCLUSION: An increase in temperature would increase the rate of AMI hospitalization.